LED light module

ABSTRACT

A light emitting module is disclosed. The light emitting module includes a lead frame body, lead frame, a heat spreader, an intermediate heat sink, and at least one light emitting element (LED). The lead frame body defines a cavity which accurately registers the heat spreader and includes optical or reflective walls surrounding the light emitting elements soldered on metallized traces of the heat spreader. The lead frame body encases and supports portions of the lead frame. The lead frame extends from outside the body into the cavity to accurately align with solder pads of the heat spreader. All the pre-aligned mechanical, thermal and electrical contacts are then soldered by solder reflow process under tight environmental control to prevent damage to the light emitting element. A robust, healthy 3-dimensional optical-electro-mechanical assembly having a very low thermal resistance in a thermal path from its light emitting element to its intermediate heatsink is created.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application claims the benefit of priority under 35 USCsections 119 and 120 of U.S. Provisional Patent Application No.61/302,474 filed Feb. 8, 2010, the entire disclosure of which isincorporated herein by reference. This patent application claims thebenefit of priority under 35 USC sections 119 and 120 of U.S.Provisional Patent Application No. 61/364,567 filed Jul. 15, 2010, theentire disclosure of which is incorporated herein by reference. Theapplicant claims benefit to Feb. 8, 2010 as the earliest priority date.

BACKGROUND

The present invention relates to light emitting devices. Moreparticularly, the present invention relates to light emitting devicemodules and lighting devices.

Light emitting diodes (LEDs) are typically made using semiconductingmaterial doped with impurities to create a P-N junction. When electricalpotential (voltage) is applied to the P-N junction current flows throughthe junction. Charge-carriers (electrons and holes) flow in thejunction. When an electron meets a hole, it falls into a lower energylevel, and releases energy in the form of light (photon, radiant energy)and heat (phonon, thermal energy).

In most applications, light is the desired form of energy from an LEDand heat is not desired. This is because heat can and often causespermanently damages to the LED, degrades LED performance by causingdecreased light output, and leads to a premature device failure.

However, in the current state of art, generation of undesired heatcannot be avoided. A typical high power LED chip of 1 mm² in area and0.10 mm in thickness has a P-N junction active layer of only 0.003 mmthick. Yet, it can convert 1 to 2 watts of electrical energy into bothradiant and thermal energy. More than 50% of electrical energy isactually converted into thermal energy which can heat up the whole LEDwithin fraction of a second. Typically, such LED operates at a junctiontemperature of 120 degrees Celsius. That is, these LEDs operate at atemperature greater than the temperature of boiling water (water boilsat 100° C.). Above 120 degrees C., the LED's forward voltage willincrease, thus resulting in higher power consumption. Also, its luminousoutput will drop correspondingly and its reliability and life expectancywill also be adversely affected.

The problem of heat is even more apparent for high power LEDs. There isan increasing demand for increasingly brighter LEDs. To make brighterLEDs, the most obvious solution is to increase the electrical powerapplied to the LEDs. This however leads to LEDs operating at evengreater temperatures. As the operating temperature increases, theefficiency of the LEDs decreases, resulting in light output that is lessthan expected or desired. That is, for example only, doubling theelectrical power of the LED does not result in the generation of twicethe amount of light. Rather, the light output is much less than theexpected twice the luminosity.

The problem of heat is compounded by the way in which the LEDs arepackaged within light emitting devices such as light bulbs. Lightemitting devices of current art (using LEDs as the core of the device)often entrap heat within the device itself. This decreases the expectedlife of the LED and of the device itself. For example, many LEDs in themarketplace are sold as having expected operating life of 50,000 hours(at which time the LED output declines to seventy percent of itsoriginal output). However, light emitting devices (having such LEDs asthe light emitting element of the device) typically specifies only35,000 hours of expected operating life).

Accordingly, there remains a need for an improved LED module thateliminates or alleviates these problems associated with heat.

SUMMARY

The need is met by the present invention. In a first embodiment of thepresent invention, a light emitting module is disclosed. The lightemitting module includes a lead frame body, lead frame, a heat spreader,and at least one light emitting element placed on the heat spreader. Thelead frame body defines a cavity. A first portion of the lead frame isencased within the lead frame body wherein the lead frame body providesstructural support and separation of leads of the lead frame. The heatspreader is positioned at least partially within the cavity of the leadframe body. The heat spreader is connected to the lead frame. At leastone light emitting element is placed on the heat spreader such that heatgenerated by the light emitting element is drawn away from the lightemitting element by the heat spreader.

In various embodiments, the light emitting module may include any one ormore the following characteristics in any combination: The lead framebody defines a reflective surface surrounding the cavity. The lead frameincludes at least two electrical conductors. The lead frame iselectrically connected to the light emitting elements on the heatspreader. A snap in body engaging second portion of the lead frame. Thelead frame body includes a first major surface, the first major surfacedefining a first plane, and wherein the lead frame is bent relative tothe first plane.

The heat spreader includes a ceramic substrate and a metal trace layerfabricated on the substrate. The substrate has a first major surface anda second major surface opposite the first major surface. The metal traceis adaptable for attaching light emitting element as well as forattaching the lead frame.

In an alternative embodiment of the heat spreader, the heat spreaderincludes a metallic substrate, a first dielectric layer above themetallic substrate, a second dielectric layer below the metallicsubstrate, a metal trace layer fabricated on the first dielectric layer,a metal layer fabricated below the second dielectric layer, and metaltrace adaptable for attaching light emitting element as well asattaching the lead frame.

The light emitting element may include light emitting junction diodeencased within resin. Alternatively, the light emitting element mayinclude light emitting diode chip.

In a second embodiment of the present invention, a light emitting moduleis disclosed. The module includes lead frame, lead frame body, and aheat spreading light emitting component. The lead frame includeselectrical conductors. The lead frame body encases first portion of thelead frame providing mechanical support to the lead frame. The leadframe body defines a cavity. The heat spreading light emitting componentincludes a thermally conductive substrate having a first major surface,and electrical traces on the first major surface of the substrate. Thelight emitting element mounted on the substrate is electricallyconnected to its metallized electrical traces. The lead frame iselectrically connected to the metallized electrical traces of the firstmajor surface of the heat spreader.

In a third embodiment of the present invention, a heat spreaderapparatus is disclosed. The heat spreader includes a metallic substrate,a first dielectric layer above the metallic substrate, a seconddielectric layer below the metallic substrate, a metal trace layerfabricated on the first dielectric layer, a metal layer fabricated belowthe second dielectric layer. The metal trace is adaptable for attachinglight emitting element and adaptable for attaching the lead frame. Themetallic substrate may include Aluminum. The first dielectric layer mayinclude Aluminum oxide. The second dielectric layer may include Aluminumoxide.

In a third embodiment of the present invention, a light emittingsubassembly is disclosed. The subassembly includes an intermediate heatsink and at least one light emitting module mounted on the intermediateheat sink. The light emitting module includes a lead frame body defininga cavity, lead frame wherein first portions of the lead frame areencased within the lead frame body, a heat spreader positioned at leastpartially within the cavity of the lead frame body, the heat spreaderconnected to the lead frame, and at least one light emitting elementplaced on the heat spreader. The heat spreader is mechanically andthermally connected to the intermediate heat sink by a robust solderjoint covering its entire bottom surface area.

In the subassembly, intermediate heat sink defines slots for engagementwith the light emitting module. The intermediate heat sink includes areflective top surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a top perspective view of a light emitting module inaccordance of one embodiment of the present invention.

FIG. 2 illustrates a bottom perspective view of the light emittingmodule of FIG. 1.

FIG. 3 illustrates a top view of the light emitting module of FIGS. 1and 2.

FIG. 4 illustrates a first side view of the light emitting module ofFIGS. 1 through 3.

FIG. 5 illustrates a second side view of the light emitting module ofFIGS. 1 through 3.

FIG. 6 illustrates a bottom view of the light emitting module of FIGS. 1and 2.

FIG. 7 illustrates a cut away side view of the light emitting module ofFIGS. 1 through 3 cut along line A-A of FIG. 3.

FIG. 8 illustrates a cut away side view of the light emitting module ofFIGS. 1 through 3 cut along line B-B of FIG. 3.

FIG. 9 is another illustration of the top view of the light emittingmodule of FIGS. 1 and 2 with portions of the light emitting modulehighlighted.

FIG. 10 is another illustration of the bottom view of the light emittingmodule of FIGS. 1 and 2 with portions of the light emitting modulehighlighted.

FIG. 11 illustrates a top perspective view of a light emitting module inaccordance of another embodiment of the present invention.

FIG. 12 illustrates a partially exploded top perspective view of thelight emitting module of FIG. 11.

FIG. 13 illustrates a partially exploded bottom perspective view of thelight emitting module of FIG. 11.

FIG. 14 illustrates an exploded side view of a first alternativeembodiment of a portion of the light emitting module.

FIG. 15 illustrates an exploded side view of a second alternativeembodiment of a portion of the light emitting module.

FIG. 16 illustrates a top perspective view of a subassembly inaccordance with another embodiment of the present invention.

FIG. 17 illustrates a bottom perspective view of the subassembly of FIG.16.

FIG. 18 illustrates a top view of the subassembly of FIGS. 16 and 17.

FIG. 19 illustrates a bottom view of the subassembly of FIGS. 16 and 17.

FIG. 20 illustrates a cut away side view of the subassembly of FIG. 18cut along line C-C.

FIG. 21 illustrates a cut away side view of the subassembly of FIG. 18cut along line D-D.

FIG. 22 illustrates a top perspective view of a subassembly inaccordance with yet another embodiment of the present invention.

FIG. 23 illustrates a top perspective view of a subassembly inaccordance with yet another embodiment of the present invention.

FIG. 24 illustrates a top perspective view of a subassembly inaccordance with yet another embodiment of the present invention.

DETAILED DESCRIPTION

The present invention will now be described with reference to theFigures which illustrate various aspects, embodiments, orimplementations of the present invention. In the Figures, some sizes ofstructures, portions, or elements may be exaggerated relative to sizesof other structures, portions, or elements for illustrative purposesand, thus, are provided to aid in the illustration and the disclosure ofthe present invention.

This patent application claims the benefit of priority of andincorporates by reference the entirety of U.S. Provisional PatentApplication No. 61/302,474 filed Feb. 8, 2010 and U.S. ProvisionalPatent Application No. 61/364,567 filed Jul. 7, 2010. Each of theseincorporated provisional applications includes drawings andspecifications including figure designations, reference numbers, anddescriptions corresponding to the figure designations and to thereference numbers. To avoid confusion and to discuss the inventions witheven more clarity, the figure designations and reference numbers used inthe incorporated documents are not used in this document. Rather, inthis document, new figure designations, reference numbers, anddescriptions corresponding to the figure designations are used.

FIG. 1 illustrates a top perspective view of a light emitting module1000 in accordance of one embodiment of the present invention. FIG. 2illustrates a bottom perspective view of the light emitting module 1000of FIG. 1. FIG. 3 illustrates a top view of the light emitting module1000 of FIGS. 1 and 2. FIG. 4 illustrates a first side view of the lightemitting module 1000 of FIGS. 1 through 3. FIG. 5 illustrates a secondside view of the light emitting module 1000 of FIGS. 1 through 3. FIG. 6illustrates a bottom view of the light emitting module 1000 of FIGS. 1and 2. FIG. 7 illustrates a cut away side view of the light emittingmodule 1000 of FIGS. 1 through 3 cut along line A-A of FIG. 3. FIG. 8illustrates a cut away side view of the light emitting module 1000 ofFIGS. 1 through 3 cut along line B-B of FIG. 3. FIG. 9 is anotherillustration of the top view of the light emitting module 1000 of FIGS.1 and 2 with portions of the light emitting module 1000 highlighted.FIG. 10 is another illustration of the bottom view of the light emittingmodule 1000 of FIGS. 1 and 2 with portions of the light emitting module1000 highlighted.

FIG. 11 illustrates a top perspective view of a light emitting module1100 in accordance of another embodiment of the present invention. Thelight emitting module 1100 has the same components and elements as thelight emitting module 1000 of FIGS. 1 through 10 with portions in adifferent configuration. FIG. 12 illustrates a partially exploded topperspective view of the light emitting module 1100 of FIG. 11. FIG. 13illustrates an exploded bottom prospective view of a first alternativeembodiment of a portion of the light emitting module 1100 of FIG. 12.FIG. 14 illustrates an exploded side view of a first alternativeembodiment of a portion of the light emitting module 1100 of FIG. 12.FIG. 15 illustrates an exploded side view of a second alternativeembodiment of a portion of the light emitting module 1100 of FIG. 12.

That is, FIGS. 1 through 10 illustrate different views of the lightemitting module 1000 of the present invention. FIGS. 11 and 12illustrate the light emitting module 1000 in a different configurationand referred to as light emitting module 1100. To avoid duplicity andconfusion, and to increase clarity, in the Figures, not every referencedportion is annotated in every Figure.

Referring to FIGS. 1 through 13, in one embodiment of the presentinvention, the light emitting module 1000 includes a lead frame body1010, lead frame 1020, at least one heat spreader 1050, and at least onelight emitting element 1080 placed on the heat spreader 1050.

Lead Frame Body

The lead frame body 1010 is typically molded plastic but can be anyother material. The lead frame body 1010 defines a cavity 1012 withinwhich the heat spreader 1050 is accurately positioned. The body cavity1012 is most clearly illustrated in FIGS. 12 and 13. In the illustratedembodiment, the heat spreader 1050 is mostly or entirely within the bodycavity 1012 (best illustrated in FIGS. 12 and 13); however, in otherembodiments, the heat spreader 1050 may be only partially concealedinside the body cavity 1012. The lead frame body 1010 can be made fromthermoplastic or thermoset plastics which can withstand hightemperatures over 200 C for a short period of time. In any event, thebody cavity 1012 is large enough to expose the light emitting element1080 while providing mechanical and structural support to the lead frame1020.

The lead frame body 1010 defines reflector surface 1014 surrounding thebody cavity 1012. In the illustrated embodiment, the body cavity 1012has a substantially rectangular shape. Accordingly, the lead frame body1010 defines four reflector surfaces 1014. However, that the number ofrectangular surfaces may vary depends on the shape of the body cavity1012. The reflector surface 1014 surrounds the body cavity 1012 whereinthe light emitting elements 1080 are placed. Consequently, the reflectorsurface 1014 reflects and redirects light (directed to it from the lightemitting elements 1080) toward a desired direction. The light directedto the reflector surface 1014 are at a very low angle (illustrated asangle 1015 in FIG. 8) and is lost in the prior art devices which aretypically MCPCB (metal-core printed circuit board) or PCB (printedcircuit board) having non-reflective flat surfaces. Consequently, theluminous efficiency of the module is higher than that of the prior art.

In the illustrated embodiment, the reflectivity of the reflector surface1014 is greater than 85 percent. To realize the reflective surface 1014,the lead frame body 1010 may include high temperature thermoplastics orthermoset plastics that are loaded with reflective materials such as,for example only, Titanium Dioxide (TiO2), Barium Sulfate (BaSO4), andothers. In one embodiment, the material used for the lead frame body1010 is a Polyphthalamide (also known as PPA, High PerformancePolyamide) with trade name as Amodel which has a reflectivity of 90percent with a low percentage of scattering.

Lead Frame

The lead frame 1020 may, but is not required to, include multiple leads,portions, or both as illustrated. In the illustrated embodiment, thelead frame 1020 is used to conduct electrical power and is a stampedmetal such as, for example only, copper or other metal alloy. Thestamped metal can be, for example, sheet metal.

In the illustrated embodiment, the lead frame 1020 includes four leadsextending from outside the lead frame body 1010, through the substanceof the lead frame body 1010, and into the body cavity 1012. In the bodycavity 1012, the lead frame 1020 makes contact with the heat spreader1050. Consequently, in the illustrated embodiment, the lead frame body1010 encases the portion of the lead frame 1020 that lies within thelead frame body 1010 as the lead frame 1020 extends from beyond the leadframe body 1010 into the body cavity 1012. This portion is referred toas the first portion. In FIGS. 9 and 10, the lead frame 1020 ishighlighted using cross hatches for even more clear illustration of thelead frame 1020 in relation to the lead frame body 1010. Such encasingconfiguration is often referred to as over molding.

For ease of discussion, various portions of the lead frame 1020 may bereferenced using an alphabetical letter following the lead framereference number 1020. For example, the portion of the lead frame 1020extending into the body cavity 1012 is referred to as the inner end1020A of the lead frame 1020. In generally, reference number 1020indicates the lead frame 1020 as a whole or in general.

The inner end 1020A of the lead frame 1020 is engaged to metal traces1052 of the heat spreader 1050. In the illustrated embodiment, the innerend 1020A of the lead frame 1020 is soldered on to the metal traces 1052of the heat spreader 1050. The soldering method can be any suitablemethod, for example, solder reflow process in which a small dot ofsolder paste is heated to its melting temperature; thus, the inner end1020A and the traces 1052 are bonded by a robust solder joint.

Here, the lead frame body 1010 acts as an alignment fixture between allthe lead frame 1020 and corresponding metal circuit traces 1052,soldering of all of the light emitting elements 1080 to the heatspreader 1050 can be done simultaneously. This simplifies the processtime and reduces the exposure of LEDs to heat more than once.Furthermore, the lead frame body 1010 provides for electrical isolationand alignment between multiple leads of the lead frame 1020.

Outer ends 1020B of the lead frame are adapted to be connected to anexternal electrical power supply. The lead frame 1020 can be bent orformed into various shape to suit the mounting requirements. Similarly,other portions 1020C may extend out of the body for other purposes suchas, for example only, mounting or engaging with additional componentsnot illustrated herein.

One embodiment of the reconfigured light emitting module 1000 of FIGS. 1and 2 are illustrated in FIGS. 11 through 13 as the light emittingmodule 1100. The light emitting module 1100 has the same elements orcomponents as the light emitting module 1000 of FIGS. 1 and 2; however,its lead frame 2010 is bent 90 degrees (orthogonal) to facilitate solderconnections with its electrical components located behind the opticalfront face of the module; and also to provide an easy engagement withthermal or mechanical component, such as, for example only, anintermediate heat sink 1090 illustrated in FIGS. 16 through 24 anddiscussed in more detail herein below. The orthogonal bent is 90 degreesrelative to a plane defined by the first major surface 1016 defined bythe lead frame body 1010. However, the degree of the bent angle is notlimited to 90 degrees in the present invention.

This bent configuration allows the light emitting module 1100 to besnapped into another assembly with its snap in body structure shown inthe Figures and discussed below. This facilitates its manufacturingprocess resulting lower manufacturing costs and times.

Once assembled with the intermediate heat sink 1090, the entireassembly, or can be the core component of general lighting applicationssuch as, for example only, and without limitation, light bulbs, lightingluminairs, street lights or parking light modules.

Snap in Body

A snap in body 1030 can be used to provide additional structural supportthe lead frame 1020 as well as electrical isolation between the leads ofthe lead frame 1020. As illustrated, the snap in body 1030 engages orsurrounds a second portion of the lead frame 1020 that is proximal tothe outer ends 1020B of the lead frame 1020. The snap in body 1030 mayinclude potions such as snap in finger 1030A to securely engage withother components such as an intermediate heat sink to be discussedbelow. A stopper 1030B portion of the snap in body 1030 allows the snapin body 1030 to be secured with a mating component such as anintermediate heat sink illustrated in FIGS. 16 through 24.

Heat Spreader

The heat spreader 1050 is connected to the lead frame 1020 as indicatedin Figures, and most clearly in FIGS. 9 and 10. The layers associatedwith the heat spreader 1050 and its connection to the lead frame 1020 isdiscussed in more detail herein below.

At least one light emitting element 1080 is placed on the heat spreader1050. In the illustrated embodiment, the light emitting module 1000includes six (6) light emitting diode packages (LEDs). Each diodepackage includes at least one light emitting chip encapsulated in anencapsulant, e.g. silicone or epoxy. In alternative embodiments, eachlight emitting element 1080 may have at least one raw light emittingchip. Each light emitting element 1080 can have a few LED chips of anycolor or a mixture of different color or size. Moreover, the differentcolors and sizes of light emitting element 1080 that can be placed onthe heat spreader 1050 is only limited by its physical and electricallimitations, and, depending on applications, can be very large.

If light emitting chips are used as the light emitting elements 1080,then die attach of chips is fabricated on the heat spreader 1050followed by wire bonding and finally by an encapsulation process. Inthis configuration, the heat spreader 1050 also serves as the substratefor multiple light emitting chips. Also, the encapsulation process canbe simple due to its large optical lens that can be placed over theentire body cavity 1012 and then filled with silicone gel to opticallycouple it to all the light emitting elements under it. The encapsulantcan be filled with phosphors to alter the wavelengths of the LED chipsmounted on the heat spreader. Or, the encapsulant can be loaded withsome fine particles of reflective materials such as, for example only,Titanium Dioxide (TiO2), Barium Sulfate (BaSO4), and others.

The heat spreader 1050 can be made of any thermally conductive material,for example, ceramics or Aluminum coated with dielectric. Other examplesof suitable materials for the heat spreader 1050 include, withoutlimitation, ceramics such as Alumina, Aluminum Nitride, or AnodizedAluminum.

Dimensions of the heat spreader 1050 can vary greatly. For example, theheat spreader 1050 may have thickness ranging from sub-millimeters (mm)to many centimeters (cm). In the illustrated embodiment, the heatspreader 1050 thickness ranges from below one (1) mm to a few mmdepending on size and requirements.

FIG. 14 illustrates an exploded side view of a first alternativeembodiment of the heat spreader 1050 and is referred to herein as theheat spreader 1050A. Referring to FIGS. 1 to 14 but mostly FIG. 14, theheat spreader 1050A includes a substrate 1054A made with ceramics. Thesubstrate 1054A has a first major surface 1056 and a second majorsurface 1058 opposite the first major surface 1056. The metal tracelayer 1052 is fabricated on the first major surface 1056. The metaltrace 1052 is adaptable for attaching light emitting elements 1080.

Additionally, the metal trace 1052 is adaptable for attaching the innerend 1020A of the lead frame 1020. Because the substrate 1054A is ceramic(thereby electrically insulating), no insulating material is needed toisolate the substrate 1054A from the traces 1052. A metal layer 1060 isfabricated on the second major surface 1058. The metal layer 1060 allowsfor solder attachment of the heat spreader 1050 to the intermediate heatsink 1090 illustrated in FIGS. 16 through 24 and discussed in moredetail herein below. Then, a solder layer 1062 is used to bond the heatspreader 1050 to the intermediate heat sink 1090. This solder layer 1062can be, but is not required to be lead free. Lead free solder hastypical thermal conductivity of approximately 57 watts per meter degreesKevin. This is significantly higher than other methods of heat contact.A solder layer 1062 is used to solder the heat spreader 1050A onto anintermediate heat sink 1090 illustrated in FIGS. 16 through 24 anddiscussed in more detail herein below. Soldering the heat spreader 1050Acreates a much better thermal contact (between the heat spreader 1050Aand the intermediate heat sink 1090) compared to the currently usedtechnique of screw attachment.

FIG. 15 illustrates an exploded side view of a second alternativeembodiment of heat spreader 1050 and is referred to herein as the heatspreader 1050B. Referring to FIGS. 1 to 15 but mostly FIG. 15, the heatspreader 1050B includes a substrate 1054B made with Aluminum. Dielectriclayers 1064 and 1066 include insulation materials such as, for example,Aluminum oxide. The insulation layers can be fabricated using anodizingprocess. This prevents the traces 1052 from shorting out. Again, thesubstrate 1054B and with its dielectric layers 1064 and 1066 has a firstmajor surface 1056 and a second major surface 1058 opposite the firstmajor surface 1056. The metal trace layer 1052 is fabricated on thefirst major surface 1056's dielectric layer 1064 using a combination ofa thin-film and plating processes. The metal trace 1052 may consist ofTitanium, Nickel, Copper, Nickel, and Gold for example only and isadaptable for soldering to the light emitting elements 1080.Additionally, the metal trace 1052 is adaptable for soldering to theinner end 1020A of the lead frame 1020.

There is no bonding adhesive needed on an anodized Aluminum for bondingthe traces 1052 to the dielectric layer 1064. In the illustratedembodiment, the thickness of Anodized layer is in the region of 33-55microns approximately. As the Aluminum oxide layers 1064 and 1066 have ahigh thermal conductivity of about 18 Watt per Meter-degree Kelvin, thethermal conductivity of the Anodized Aluminum is much higher compared tothe thermal conductivity of MCPCB (metal-core printed circuit boards)often used in the prior art lighting modules. The existing designs usingMCPCB typically has lower thermal conductivity of less than 2 Watt perMeter-degree Kelvin. Accordingly, the present invention provides forhigher thermal conductivity to remove heat away from the light emittingelements 1080 compared to that of the existing art.

An anodized aluminum heat spreader 1050B uses its aluminum oxide layer1064 and 1066 as natural dialectical layers. In contrast, MCPCB of theprior art uses organic dielectric layers as a dielectric.

In the illustrated embodiment, the anodized Aluminum oxide dielectriclayers 1064 and 1066 are approximately 33 microns to 55 microns thickand their thermal conductivity is approximately 18 Watt per Meter-degreeKelvin. In contrast, the organic dielectric layers of MCPCB as typically75 microns to 125 microns thick and their thermal conductivity is in therange of approximately 2 Watt per Meter-degree Kelvin. Hence, anodizedAluminum heat spreader 1050 of the present invention has a much superiorthermal conducting performance.

A metal layer 1060 is fabricated on the second major surface 1058'sdielectric layer 1066. Again, the metal layer 1060 allows for solderattachment of the heat spreader 1050 to the intermediate heat sink 1090.A solder layer 1062 is used to solder the heat spreader 1050B onto anintermediate heat sink 1090 illustrated in FIGS. 16 through 24 anddiscussed in more detail herein below. Soldering the heat spreader 1050creates a much better thermal contact (between the heat spreader 1050and the intermediate heat sink 1090) compared to the currently usedtechnique of screw attachment with less contact surface area and with ahigh interface resistance.

In one example embodiment, the heat spreader 1050 is made of Aluminumwith a top surface area of 174 mm² and a thickness of 0.63 mm. With sixlight emitting elements 1080 soldered on the metal traces 1052, eachrequiring about 1 mm² area, the surface area ratio of the heat spreader1050 to that of the light emitting elements 1080 is 174 to 6, orapproximately 29 to 1. As such, its thermal spreading resistance isalmost zero.

The heat spreader 1020 and the light emitting elements 1080, combined,are referred to herein as the heat spreading lighting component.

Intermediate Heat Sink

FIG. 16 illustrates a top perspective view of a light emittingsubassembly 1200 in accordance with another embodiment of the presentinvention. FIG. 17 illustrates a bottom perspective view of the lightemitting subassembly 1200 of FIG. 16. FIG. 18 illustrates a top view ofthe light emitting subassembly 1200 of FIGS. 16 and 17. FIG. 19illustrates a top view of the light emitting subassembly 1200 of FIGS.16 and 17. FIG. 20 illustrates a cut away side view of the lightemitting subassembly 1200 of FIG. 18 cut along line C-C. FIG. 21illustrates a cut away side view of the light emitting subassembly 1200of FIG. 18 cut along line D-D.

Referring to FIGS. 16 through 21, the subassembly 1200 includes anintermediate heat sink 1090 and at least one light emitting module 1100mounted on the intermediate heat sink 1090. The light emitting module1100 is the same light emitting module of FIGS. 11 through 13 anddiscussed herein above in more detail.

The intermediate heat sink 1090 is soldered (structurally and thermallyconnected) to the heat spreader 1050. The heat spreader 1050, in turn,is soldered (structurally and thermally connected) to the light emittingelements 1080. This is most clearly illustrated in FIGS. 20 and 21.Accordingly, heat generated by the light emitting elements 1080 is drawnaway from the light emitting elements 1080 by the heat spreader 1050.The heat is then drawn away from the heat spreader 1050 by theintermediate heat sink 1090.

The intermediate heat sink 1090 may have any shape and size depending onthe final product design requirements. In the illustrated embodiment,the intermediate heat sink 1090 is made of metal such as, for exampleonly, copper alloy or aluminum alloy, and can be plated with nickel.Such plating allows for easier soldering of the heat spreader 1050 tothe intermediate heat sink 1090. The intermediate heat sink 1090 definesslots 1094 to allow portions of the light emitting module 1100 to passthrough the slots and thereby engage the intermediate heat sink 1090.Further, the slots 1094 aid in alignment of the intermediate heat sink1090 to the light emitting module 1100. Using this alignment technique,the manufacturing process is less labor intensive compared to themanufacturing process of the existing products. This results in higheryield and lower cost of assembly.

The intermediate heat sink 1090 is covered by an optical reflectiveelement or itself coated with reflective materials on the top side 1092to form a reflective bowl to reflect and recycle light therebyminimizing loss of light. The reflective material or component may havea mirror finished Aluminum or a silver coating having thickness of a fewAngstroms.

In the illustrated embodiment, the heat generated by the light emittingelements 1080 is drawn away from the light emitting elements 1080 by theheat spreader 1050 that spreads the heat into its own body which has amuch greater thermal mass than the light emitting elements 1080. Furtherdown along the thermal path, the heat is conducted to the intermediateheat sink 1090 which dimensions and surface areas are many times that ofthe heat spreader 1050. Consequently, the heat generated by the lightemitting elements 1080 is effectively removed from the light emittingelements 1080 thereby reducing adverse effects of heat on the lightemitting elements 1080 such as reduction of luminous output, damage tothe LED chips, and ultimately shortened service life.

FIG. 22 illustrates a top perspective view of a light emittingsubassembly 1300 in accordance with another embodiment of the presentinvention. Referring to FIG. 22, the subassembly 1300 includes anintermediate heat sink 1310 and at least one light emitting module 1100mounted on the intermediate heat sink 1310. The light emitting module1100 is the same light emitting module of FIGS. 11 through 13 anddiscussed herein above in more detail.

The intermediate heat sink 1310 is substantially flat in the illustratedembodiment as opposed to a bowl shaped intermediate heat sink 1090 (ofFIGS. 16 through 21). Further, the intermediate heat sink 1310 generallyhas a flat cylindrical shape. However, the intermediate heat sink 1310is similar to the intermediate heat sink 1090 (of FIGS. 16 through 21)in composition and function. For example, the intermediate heat sink1310 is made of thermally conductive material such as metal alloy.Further, the intermediate heat sink 1310 has a top surface 1312 that iscoated with reflective material. Also, the intermediate heat sink 1310defines slots 1314 used to aid in the engagement of and alignment withthe intermediate heat sink 1310 with the one light emitting module 1100.

FIG. 23 illustrates a top perspective view of a light emittingsubassembly 1400 in accordance with yet another embodiment of thepresent invention. Referring to FIG. 23, the subassembly 1400 includesan intermediate heat sink 1410 and at least one light emitting module1100 mounted on the intermediate heat sink 1410. The light emittingmodule 1100 is the same light emitting module of FIGS. 11 through 13 anddiscussed herein above in more detail.

The intermediate heat sink 1410 is substantially flat in the illustratedembodiment as opposed to a bowl shaped intermediate heat sink 1090 (ofFIGS. 16 through 21). Further, the intermediate heat sink 1410 generallyhas a rectangular prism shape. However, the intermediate heat sink 1410is similar to the intermediate heat sink 1090 (of FIGS. 16 through 21)in composition and function. For example, the intermediate heat sink1410 is made of thermally conductive material such as metal alloy.Further, the intermediate heat sink 1410 has a top surface 1412 that iscovered with an optical reflective element or itself coated withreflective material. Also, the intermediate heat sink 1410 defines slots1414 used to aid in the engagement of and alignment with theintermediate heat sink 1410 with the one light emitting module 1100.

FIG. 24 illustrates a top perspective view of a light emittingsubassembly 1500 in accordance with yet another embodiment of thepresent invention. Referring to FIG. 24, the subassembly 1500 includesan intermediate heat sink 1510 and at least one light emitting module1100 mounted on the intermediate heat sink 1510. In fact, in theillustrated embodiment, the light emitting subassembly 1500 includes twolight emitting modules 1100. The light emitting module 1500 is the samelight emitting module of FIGS. 11 through 13 and discussed herein abovein more detail.

Again, the intermediate heat sink 1510 is substantially flat in theillustrated embodiment as opposed to a bowl shaped intermediate heatsink 1090 (of FIGS. 16 through 21). Further, the intermediate heat sink1510 generally has a rectangular prism shape. However, the intermediateheat sink 1510 is similar to the intermediate heat sink 1090 (of FIGS.16 through 21) in composition and function. For example, theintermediate heat sink 1510 is made of thermally conductive materialsuch as metal alloy. Further, the intermediate heat sink 1510 has a topsurface 1512 that is covered with an optical reflective element oritself coated with reflective material. Also, the intermediate heat sink1510 defines slots 1514 used to aid in the engagement of and alignmentwith the intermediate heat sink 1510 with the one light emitting module1100.

The intermediate heat sink 1090, 1310, 1410, 1510 transfers heat fromthe heat spreader 1050 to an ultimate heat sink. The ultimate heat sink,in many applications, is the body of the lighting device such as thelight bulb that includes light emitting subassembly 1200, 1300, 1400,and 1500. At the body of the lighting device, the heat is dissipated,often by convention to the surrounding air, or even to other heatdissipating mechanisms such as an external heat sink.

Thermal Path

Referring to FIGS. 1 through 24, and more specifically to FIGS. 16through 24, as illustrated, the thermal path of heat generated by thelight emitting elements 1080 is drawn away from the light emittingelements 1080 by the heat spreader 1050 that spreads the heat into itsown body which has a much greater thermal mass than the light emittingelements 1080. At the same time, the heat is then conducted to theintermediate heat sink 1090 which has even greater dimensions than thedimensions of the heat spreader 1020 as well as much greater surfacearea. Consequently, the heat generated by the light emitting elements1080 is effectively removed from the light emitting elements 1080thereby reducing adverse effects of heat on the light emitting elements1080 such as reduction of luminous output, damage to the light emittingelements 1080, and ultimately shortened service life.

For subassemblies 1200, 1300, 1400, 1500 where its included heatspreader 1050A has the configuration illustrated in FIG. 14, the thermalpath from the light emitting elements 1080 to the intermediate heat sink1090, 1310, 1410, 1510 is as follows: the heat flux flows from lightemitting element 1080 in the following sequence to the solder, the metaltraces 1052, the ceramic substrate 1054A, the metal layer 1060, thesolder 1062, and finally to the intermediate heat sink 1090, 1310, 1410,1510.

For subassemblies 1200, 1300, 1400, 1500 where its included heatspreader 1050B has the configuration illustrated in FIG. 15, the thermalpath from the light emitting elements 1080 to the intermediate heat sink1090, 1310, 1410, 1510 is as follows: the light emitting element 1080 tosolder to metal traces 1052 to dielectric layer 1064 to substrate 1054Bto dielectric layer 1066 to metal layer 1060 to solder 1062 to theintermediate heat sink 1090, 1310, 1410, 1510.

For example, in experiments and test, it has been demonstrated that anAlumina heat spreader 1050 having a top surface area of approximately150 square mm and a thickness of 0.63 mm, can effectively providenegligible spreading thermal resistance for a six light emittingelements, each element including 1 to 2 watt LED packages. Only whereLED chips are clustered very close together, a better thermal conductiveceramics such as AlN or anodized aluminum is used.

Assembly, Construction, and Additional Advantages

Referring to FIGS. 1 through 24, and more specifically to FIGS. 14, 15,20, and 21, it has already been discussed that the light emittingelements 1080 are soldered onto the metal traces 1052 of the lightemitting modules 1000 and 1100 and that the heat spreader 1050 issoldered onto the intermediate heat sinks 1090, 1310, 1410, and 1510.

In the present invention, the illustrated designs allow for use ofsolder reflow technique to solder all the light emitting elements 1080to the metal traces 1052 and all the lead frame 1020 and heatsinkspreader 1050 to the intermediate heatsink 1090, 1310, 1410 or 1510 allat the same time. That is, only one or at most two soldering cycles arerequired to solder all the light emitting elements 1080 to form athermally efficient subassembly. This is a significant advantage overthe existing art where hot-bar soldering technique are necessary tosolder loose wires from power supply to a MCPCB (metal core printedcircuit board) where light emitting diode packages are soldered first.Further, in the present invention, during a single or two solder reflowcycles, the light emitting elements 1080 are exposed only to itsallowable peak temperature and time duration, hence protected fromoverheating and over exposure. These factors reduce the risk of damaginglight emitting elements 1080 during the manufacturing process.

Also, in manufacturing, the first solder reflow process can be carriedout to solder all light emitting elements 1080 to the heat spreader1050, then the second solder reflow process is to solder the heatspreader 1050 to lead frame 1020 and the intermediate heat sink all atonce. The same solder alloy can be used for both reflow processesbecause the solder from the first solder reflow has absorbed othermetals as impurities and will not melt during the second solder reflow.Hence, the light emitting elements 1080 will not be unsoldered duringthe second reflow by the same eutectic soldering temperature again.

The present invention has a number of potential applications includinglighting products such as light bulbs of any wattage and of variousluminous performance and physical size and connection. Such device canbe built more cheaply than the existing technology having the sameluminous performance. Its 3-dimensional modular design can serve as alight engine for any conceivable lighting product such as street light,stadium light, industrial light, security light or any illuminationproduct.

CONCLUSION

From the foregoing, it will be appreciated that the present invention isnovel and offers advantages over the existing art. Although a specificembodiment of the present invention is described and illustrated above,the present invention is not to be limited to the specific forms orarrangements of parts so described and illustrated. For example,differing configurations, sizes, or materials may be used to practicethe present invention.

I claim:
 1. A light emitting module, the module comprising: a lead framebody, said lead frame body defining a cavity; lead frame wherein firstportions of said lead frame are encased within said lead frame body, andsaid lead frame having second portions; a heat spreader positioned atleast partially within the cavity of said lead frame body, said heatspreader connected to said lead frame; at least one light emittingelement placed on said heat spreader; and a first snap in body engagingthe second portions of said lead frame.
 2. The module recited in claim 1where said lead frame body includes a first major surface, the firstmajor surface defining a first plane, and wherein said lead frame isbent relative to the first plane.
 3. A light emitting module, the modulecomprising: a lead frame body, said lead frame body defining a cavity;lead frame wherein first portions of said lead frame are encased withinsaid lead frame body; a heat spreader positioned at least partiallywithin the cavity of said lead frame body, said heat spreader connectedto said lead frame; at least one light emitting element placed on saidheat spreader; wherein said heat spreader comprises: a ceramic substratehaving a first major surface and a second major surface opposite thefirst major surface; a metal trace layer fabricated on the first majorsurface; said metal trace adaptable for attaching light emittingelement; and said metal trace adaptable for attaching said lead frame.4. A light emitting module, the module comprising: a lead frame body,said lead frame body defining a cavity; lead frame wherein firstportions of said lead frame are encased within said lead frame body; aheat spreader positioned at least partially within the cavity of saidlead frame body, said heat spreader connected to said lead frame; atleast one light emitting element placed on said heat spreader; whereinsaid heat spreader comprises: a metallic substrate; a first dielectriclayer above said metallic substrate; a second dielectric layer belowsaid metallic substrate; a metal trace layer fabricated on the firstdielectric layer; a metal layer fabricated below the second dielectriclayer; said metal trace adaptable for attaching light emitting element;and said metal trace adaptable for attaching said lead frame.
 5. Themodule recited in claim 4 wherein said light emitting element compriseslight emitting diode (LED) encased within resin.
 6. The module recitedin claim 5 first comprising a first LED emitting light having a firstcolor and a second LED emitting light having a second color.
 7. Themodule recited in claim 4 wherein said light emitting element compriseslight emitting diode (LED) chip.
 8. The module recited in claim 7 firstcomprising a first LED chip emitting light having a first color and asecond LED chip emitting light having a second color.
 9. The modulerecited in claim 7 first comprising encapsulant encasing the LED chip.10. The module recited in claim 9 wherein said encapsulant includingphosphors to modify wavelengths of light emitted by said LED chip. 11.The module recited in claim 9 wherein said encapsulant includingdiffusant to diffuse light emitted by said LED chip.
 12. A lightemitting subassembly, subassembly comprising: an intermediate heat sink;at least one light emitting module mounted on said intermediate heatsink; wherein said light emitting module comprises: a lead frame bodydefining a cavity; lead frame wherein first portions of said lead frameare encased within said lead frame body; a heat spreader positioned atleast partially within the cavity of said lead frame body, said heatspreader connected to said lead frame; at least one light emittingelement placed on said heat spreader; wherein said heat spreader isthermally connected to said intermediate heat sink; and wherein saidintermediate heat sink defines slots for engagement with said lightemitting module.